In the field of micro-electromechanical systems (MEMS), gold (Au) is generally used as the pad material in order to reduce the pad resistance. But, the bonding force between gold and a substrate (e.g., silicon) is relatively poor, which affects the performance of the pad. Therefore, an adhesive layer, e.g., chromium (Cr) is formed between gold and the substrate. However, chromium (Cr) will react with silicon (Si) to form SiCr that has a relatively high electrical resistance, so that the contact resistance between the pad and the substrate is relatively high.
Thus, there is a need for a semiconductor device having an improved pad structure and manufacturing method for reducing the electrical resistance between a pad and a substrate of the semiconductor device.